SOIL, MIlsrilfG AREAS, AND MINERALS. 13 



the foothill region. They stretch northward and form most of the foothills, but are 

 there commonly deeply buried under gravel and bowlder drift. They also occur 

 along Boulder River, (as far up as the central areas, and at the head of Stillwater 

 River in the Cooke City region. There are also outcropping strata of limestones in 

 the southwestern portion of the reserve, in Slough Creek Valley, on Buffalo Plateau, 

 and farther westward. The lavas occur throughout all the areas west and northwest 

 from Cooke City. For the most part they have been ejected from vents or 

 craters in the region around Haystack Peak at the head of Boulder River. In part 

 they are brecciated lavas and probably ejected through fissures. There is also a 

 large field of these lavas in the northern part of the reserve, beginning on the left 

 bank of Stillwater River, in the southeast corner of T. 4 N., R. 15 E., whence it 

 stretches northward and eastward 10 to 25 miles. 



The soil in the area is of two principal varieties, a siliceous loam derived from 

 the disintegration of the prevailing granitic rocks with admixtures of mold and vege- 

 (f'lble debris, and gumbo soils derived from the decomposition of the modern lavas. 

 The former soils are more common and occur throughout the reserve; the latter are 

 confined to the areas where they are underlain by rocks from which they were 

 derived. 



The siliceous soils are generally poor, except in swales and depressions, where 

 large accumulations of vegetable mold have been washed in from the surrounding 

 high ground. In most places the surface of the soil is strewn with bowlders. The 

 substratum or basement is always composed of sand and gravel with bowlders freely 

 interspersed, the whole easily displaced ,and gullied when the turf or forest on its 

 surface is from any cause destroyed or removed. 



The^umbo soils are hard and tough when dry, but when wet dissolve almost 

 like soap and are easily gullied and washed. Wherever these soils occur in the non- 

 timbered or woodland areas of the foothills and have been denuded by excessive 

 pasturing, gullying is taking place. They possess a much greater degree of fertility 

 than the .siliceous soils, and in the forested areas bear the heaviest stands of timber in 

 the reserve. / 



MINIl^Cx AREAS AND MINERAIiS. 



The area discussed contains several mineralized areas and mining camps, in 

 some of which more or less activity is displayed in the extraction of ore, while in 

 others no mining operations are now being carried on. The principal mining 

 districts are as follows: Boulder Riiver, to its head in the region around Haystack 

 Peak; the divides at the head of Stillwater River; the southern and main 

 tributaries of Clark Fork and Soda Butte Creek, a district with Cooke City as its 

 center; Horseshoe Mountain, a small tract between upper Slough Creek and 

 Stillwater River; the centjal areas of the Stillwater Valley around Nye and the 



